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WO2008136814A2 - Traitement de l'eau par filtration améliorée par des dendrimères - Google Patents

Traitement de l'eau par filtration améliorée par des dendrimères Download PDF

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Publication number
WO2008136814A2
WO2008136814A2 PCT/US2007/024656 US2007024656W WO2008136814A2 WO 2008136814 A2 WO2008136814 A2 WO 2008136814A2 US 2007024656 W US2007024656 W US 2007024656W WO 2008136814 A2 WO2008136814 A2 WO 2008136814A2
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Prior art keywords
dendrimer
dendrimers
binding
water
pamam
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WO2008136814A3 (fr
Inventor
Mamadou S. Diallo
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California Institute of Technology
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California Institute of Technology
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Priority claimed from US11/888,498 external-priority patent/US20080185341A1/en
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Publication of WO2008136814A3 publication Critical patent/WO2008136814A3/fr
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/68—Treatment of water, waste water, or sewage by addition of specified substances, e.g. trace elements, for ameliorating potable water
    • C02F1/683—Treatment of water, waste water, or sewage by addition of specified substances, e.g. trace elements, for ameliorating potable water by addition of complex-forming compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds
    • B01J20/265—Synthetic macromolecular compounds modified or post-treated polymers
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
    • C02F1/56—Macromolecular compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/48—Antimicrobial properties
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
    • C02F2001/422—Treatment of water, waste water, or sewage by ion-exchange using anionic exchangers
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
    • C02F2001/425—Treatment of water, waste water, or sewage by ion-exchange using cation exchangers
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/101—Sulfur compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/06—Contaminated groundwater or leachate
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/18—Removal of treatment agents after treatment
    • C02F2303/185—The treatment agent being halogen or a halogenated compound

Definitions

  • the invention relates to the fields of dendrimer chemistry, ion exchange, ultrafiltration, and water purification.
  • Clean water is essential to human health, and is a critical feedstock in the electronics, pharmaceutical and food industries. Treatment of groundwater, lake and reservoir water is often required to make water safe for human consumption. For wastewater, treatment is necessary to remove harmful pollutants from domestic and industrial liquid waste so that it is safe to return to the environment.
  • Current water treatment systems are generally large, centralized systems that employ a number of steps, including treatment with anaerobic organisms, oxidizers, chlorine, and flocculants.
  • DOT-NET distributed optimal technology networks
  • micellar-enhanced ultrafiltration (MEUF) (Scamehorn and Harwell, (1988) In Surfactant Based Separation Processes, Surfactant Science Series, VoI 33, Marcel Dekker, New York, Dunn et al., (1989) Coll. Surf. 35:49, Baek et al., (2004) J. Haz. Mater. 1081 :19, Richardson et al., (1999) J. Appl. Polym. Sci.
  • MEUF micellar-enhanced ultrafiltration
  • CMC critical micelle concentration
  • micellar surfactant solutions to remove organic pollutants from contaminated groundwater and industrial wastewater
  • a typical micellar enhanced ultrafiltration (MEUF) process a surfactant or an amphiphilic block copolymer is added to contaminated water (Dunn, R.O., Jr., et al. (1985), Sep.
  • micellar solution is then passed through an ultrafiltration membrane with pore sizes smaller than those of the organic laden micelles.
  • Micelles are non-covalently bonded aggregates, and their formation involves free energies of the order of 1 ORT (where R is the ideal gas constant and T is the solution temperature). Accordingly, they tend to be dynamic and flexible structures with finite lifetime (Puwada, S. and Blankschtein, D., (1990), J. Chem. Phys., 92:3710-3724, Israelachvili, J. N.
  • Typical micelles solubilize organic solutes through partitioning into their hydrophobic core, and bind metal ions through electrostatic interactions with negatively-charged head- groups.
  • MEUF processes are not very selective and have relatively low capacity.
  • surfactant solutions with redox, catalytic and biocidal activity remains a major challenge.
  • MEUF has remained for the most part a separation process with limited practical applications.
  • the PSUF process was designed to remove metal ions from contaminated wastewater streams.
  • the technology uses water-soluble polymers prepared with selective receptor sites to sequester metal ions, organic molecules, and other species from dilute aqueous solutions.
  • the water-soluble polymers are designed with a large enough molecular size that they can be separated and concentrated using ultrafiltration (UF) methods. Water and small, unbound components of the solution pass freely through the UF membrane while the polymer and its load of bound contaminants remains in the retentate.
  • PSUF uses soluble high-mass linear polymers such as polyethyleneimine and polyacrylic acid, or polymers bearing chelating groups such as EDTA or cyclams, that exhibit chelation properties toward the metal(s) of interest.
  • PSUF process Principal drawbacks of the PSUF process are the fouling of the separation membrane by aggregated polymer, the low specificity and fixed properties of bare polyethyleneimine and polyacrylic acid, and the high cost of derivatized polymers bearing chelating moieties. As a result, practical uses of PSUF are largely limited to high-value applications, such as precious metal recovery and nuclear fuel and nuclear waste processing.
  • Ion exchange is presently the method of choice, using either nonselective resins or selective resins. See Gu, B. and Brown, G. M. "Recent advances in ion exchange for perchlorate, treatment, recovery and destruction" In Perchlorate Environmental Occurrence, Interactions and Treatment, Gu, B. and Coates, J. D., Eds.; Springer: New York, 2006; see also Tripp, A. R. and Clifford. D. A. "Ion exchange for the remediation of perchlorate-contaminated drinking water” J. Am. Water Works Assn. 2006, 98:105-114.
  • the non-selective resins are inexpensive, but require frequent regenerations with brine (6-12% NaCl solution) due to their low ClO 4 " capacity and selectivity. This generates a large volume of perchlorate-containing brine that presents disposal and waste-treatment problems of its own.
  • the ClO 4 " selective resins do not require frequent regenerations, but because of their strong binding affinity for ClO 4 " , they are not readily regenerated. In the absence of a regeneration cycle, and despite their relatively high cost, spent C10 4 " -selective resins are usually incinerated following a single use. Regeneration of ClO 4 " selective resins with concentrated acidic ferric chloride has been demonstrated, but the subsequent high-temperature treatment of the regenerant solution presents yet another set of capital expense, operating costs, and disposal problems.
  • the invention provides improved dendrimer-assisted methods of removing one or more dissolved species (solutes) from aqueous fluids, by contacting the fluid with an amount of a dendrimer agent sufficient to bind at least a portion of the dissolved species to produce a quantity of dendrimer-bound solute, and filtering the dendrimer-bound solute from the fluid, whereby a quantity of filtered fluid with a reduced level of dissolved species is produced.
  • Preferred embodiments provide methods wherein the filtering process employs a filter selected from the group consisting of nanofilters, ultrafilters, microfilters, and combinations thereof. Further preferred embodiments comprise the application of pressure, vacuum, gravity, and combinations thereof to accelerate the filtration process.
  • Certain embodiments of the invention provide methods wherein at least one solute is copper, cobalt, nickel, lead, cadmium, zinc, mercury, iron, chromium, silver, gold, cadmium, iron, palladium, platinum, gadolinium, uranium, or arsenic, and the dendrimer is a cation- binding dendrimer that binds the ions of at least one metal selected from the group consisting of copper, cobalt, nickel, lead, cadmium, zinc, mercury, iron, chromium, silver, gold, cadmium, iron, palladium, platinum, gadolinium, uranium, and arsenic, and combinations thereof.
  • dendrimer-bound solute is subjected to a recycling reaction to separate at least a portion of the solute from at least a portion of the dendrimer-bound solute to produce a quantity of solute and a quantity of unbound dendrimers, and further comprising re-using the unbound dendrimers in the overall process.
  • Another embodiment of the invention relates to a water filtration system, comprising a reaction unit including a quantity of a dendrimer agent and a filtration unit in fluid communication with the reaction unit.
  • Still further embodiments relate to a water filtration system
  • a dendrimer recovery unit in fluid communication with the filtration unit and configured to implement a recycling reaction to recycle a quantity of dendrimers.
  • the dendrimer-bound ions are released from the dendrimer agent, and the dendrimer agent thus obtained is filtered from the released ions by any of the filtration methods described herein, and re-used in the reaction unit.
  • the filtration unit and the dendrimer recovery unit may optionally be integrated.
  • Certain embodiments of the invention relate to a method of binding contaminants in water, comprising providing a quantity of contaminated water, and contacting the contaminated water with a dendrimer agent.
  • Certain embodiments of the invention relate to the removal of an anion from water by contacting the water with at least two dendrimer agents, one of which preferentially binds to the anion.
  • the anion is perchlorate, which is removed from water by contacting perchlorate-containing water with a dendrimer agent having binging affinity for perchlorate ions, in the presence of one or more additional dendrimer agents having binding affinity for ions other than perchlorate.
  • the water is contacted with at least a second dendrimer agent having binding affinity for sulfate ions.
  • the dendrimer agent may comprise a quantity of a tecto-dendrimer or linear-dendritic copolymer, and the dendrimer agent may also comprise a quantity of a dendrimer selected from the group consisting of cation-binding dendrimers, anion-binding dendrimers, organic compound-binding dendrimers, redox-active dendrimers, biological compound-binding dendrimers, catalytic dendrimers, biocidal dendrimers, viral-binding dendrimers, multi-functional dendrimers, and combinations thereof.
  • Figure 1 shows a sample embodiment of a dendrimer-enhanced filtration system in accordance with an embodiment of the present invention.
  • Figure 2 shows examples of different types of dendrimers.
  • Figure 3 shows an example of a composite solid-supported filter for purification of water contaminated by mixtures of cations, anions, organic/inorganic solutes, bacteria and viruses.
  • Figure 4 shows some examples of structures of PAMAM dendrimers with EDA core and NH 2 terminal groups.
  • Figure 5 A shows the extent of binding of Cu(II) in aqueous solutions to EDA core G4-NH 2 PAMAM dendrimers as a function of metal ion dendrimer loading and solution pH, in accordance with an embodiment of the present invention.
  • Figure 5B shows the extent of binding of Cu(II) in aqueous solutions to G4- Ac(NHCOCH 3 ) PAMAM dendrimers as a function of metal ion dendrimer loading and solution pH, in accordance with an embodiment of the present invention.
  • Figure 6 shows the fit of a two-site model of Cu(II) uptake by G4-NH 2 PAMAM dendrimer in aqueous solutions plotted against the measured extent of binding at room temperature and pH 7.0.
  • Figure 7A shows the retention of EDA core G3-NH 2 , G4-NH 2 , and G5-NH 2 PAMAM dendrimers in aqueous solutions as a function of solution pH using a regenerated cellulose membrane, in accordance with an embodiment of the present invention.
  • Figure 7B shows the retention of EDA core G3-NH 2 , G4-NH 2 , and G5-NH 2 PAMAM dendrimers in aqueous solutions as a function of solution pH using a polyethersulfone membrane, in accordance with an embodiment of the present invention.
  • Figure 8 A shows Cu(II) retention in aqueous solutions of EDA core G4-NH 2 PAMAM dendrimers as a function of solution pH and molecular weight cut-off using a regenerated cellulose membrane, in accordance with an embodiment of the present invention.
  • Figure 8B shows Cu(II) retention in aqueous solutions of EDA core G4-NH 2 PAMAM dendrimers as a function of solution pH and molecular weight cut-off using a polyethersulfone membrane, in accordance with an embodiment of the present invention.
  • Figure 8C shows Cu(II) retention in aqueous solutions of EDA core G3-NH 2 , G4- NH 2 , and G5-NH 2 PAMAM dendrimers as a function of demdrimer type and membrane chemistry, in accordance with an embodiment of the present invention.
  • Figure 9A shows the permeate flux in aqueous solutions of Cu(II) + EDA Core G4- NH 2 PAMAM at pH 7, with a 10 kD cut-off regenerated cellulose membrane, in accordance with an embodiment of the present invention.
  • Figure 9B shows the permeate flux in aqueous solutions of Cu(II) + EDA Core G4- NH 2 PAMAM dendrimer as a function of solution pH and molecular weight cut-off with a regenerated cellulose membrane, in accordance with an embodiment of the present invention.
  • Figure 9C shows the permeate flux in aqueous solutions of Cu(II) + EDA Core G4- NH 2 PAMAM dendrimer as a function of solution pH and molecular weight cut-off with a polyethersulfone membrane, in accordance with an embodiment of the present invention.
  • Figure 9D shows the permeate flux in aqueous solutions of Cu(II) + EDA Core G3- NH 2 , G4-NH2, and G5-NH 2 PAMAM dendrimers at pH 7 with a polyethersulfone membrane, in accordance with an embodiment of the present invention.
  • Figure 1OA shows normalized permeate flux in aqueous solutions of Cu(II) + EDA core G4-NH 2 PAMAM dendrimer as a function of solution pH and molecular weight cut-off with a regenerated cellulose membrane, in accordance with an embodiment of the present invention.
  • Figure 1OB shows normalized permeate flux in aqueous solutions of Cu(II) + EDA core G3-NH 2 , G4-NH 2 , and G5-NH 2 PAMAM dendrimers at pH 7 with a 10 kD molecular weight cut-off regenerated cellulose membrane, in accordance with an embodiment of the present invention.
  • Figure 1OC shows normalized permeate flux in aqueous solutions of Cu(II) + EDA core G4-NH 2 PAMAM dendrimers as a function of solution pH and molecular weight cut-off with a polyethersulfone membrane, in accordance with an embodiment of the present invention.
  • Figure 1OD shows normalized permeate flux in aqueous solutions of Cu(II) + EDA core G3-NH 2 , G4-NH 2 , and G5-NH 2 PAMAM dendrimers at pH 7 with a 10 kD molecular weight cut-off polyethersulfone membrane in accordance with an embodiment of the present invention.
  • Figure 11 shows the extent of binding of Co(II) in aqueous solutions of EDA core G4- NH 2 PAMAM dendrimer at room temperature as function of solution pH and metal ion dendrimer loading, in accordance with an embodiment of the present invention.
  • Figure 12 shows the extent of binding of Ag(I) in aqueous solutions of EDA core G4- NH 2 PAMAM dendrimer at room temperature as function of solution pH and metal ion dendrimer loading, in accordance with an embodiment of the present invention.
  • Figure 13 shows the extent of binding of Fe(III) in aqueous solutions of EDA core G4-NH 2 PAMAM dendrimer at room temperature as function of solution pH and metal ion dendrimer loading, in accordance with an embodiment of the present invention.
  • Figure 14 shows the extent of binding of Ni(II) in aqueous solutions of EDA core G4- NH 2 PAMAM dendrimer at room temperature as function of solution pH and metal ion dendrimer loading, in accordance with an embodiment of the present invention.
  • Figure 15 shows the extent of binding of perchlorate in aqueous solutions of G5-NH 2 DAB core PPI dendrimer, in accordance with an embodiment of the present invention.
  • Figure 16 shows the effect of pH on the extent of binding of perchlorate to G5-NH2 PPI dendrimer in deionized water at an initial perchloration concentration of 1000 ppb (0.01 mM).
  • Figure 17 shows the effect of pH on the fractional binding of perchlorate to G5-NH2 PPI dendrimer in deionized water at at an initial perchloration concentration of 1000 ppb (0.01 mM).
  • Figure 18 compares the extent of binding of perchlorate to G5-NH2 PPI and G4-NH2 PAMAM dendrimers at an initial perchloration concentration of 1000 ppb (0.01 mM).
  • Electrolyte 1 containins 0.1 mM NaCl, 0.3 mM NaHCC ⁇ , 0.1 mM NaNO3 and 0.1 mM Na2SO4; Electrolyte 2 contains 1.0 mM NaCl, 3.0 mM NaHCO3, 1.0 mM NaNC-3 and 1.0 mM Na2SO4.
  • Figure 20 shows the effect of added G4-NH2 PAMAM dendrimer on the extent of binding of 1000 ppb perchlorate to G5-NH2 PPI dendrimer in deionized water and in model electrolyte.
  • Figure 21 shows the extent of binding of 1000 ppb perchlorate to G5-NH2 PPI dendrimer in deionized water and model electrolyte solution as measured at 1 , 4, and 24 hours.
  • Figure 23 A shows the reductive dehalogenation of perchloroethylene in aqueous solutions of Fe(O) EDA core G4-NH 2 PAMAM dendrimer nanocomposites in accordance with an embodiment of the present invention.
  • the diamonds represent the amounts of perchloroethylene, and the squares represent the amounts of trichloroethylene.
  • Figure 23B shows the reductive dehalogenation of perchloroethylene in aqueous solutions with Fe(O) in the absence of EDA core G4-NH 2 PAMAM dendrimers, in accordance with an embodiment of the present invention.
  • the diamonds represent the amounts of perchloroethylene, and the squares represent the amounts of trichloroethylene.
  • the invention disclosed herein relates generally to materials and methods for the removal of solutes from aqueous fluids.
  • the materials and methods of the invention are useful for the removal of contaminants from water. For that reason, the invention will be discussed for the most part in terms of water and contaminants, but it should be understood that the materials and methods of the invention are not limited to those particular embodiments but are applicable to other fluids and solutes.
  • suspended nanoscale particles such as bacteria and viruses, are considered to be "solutes".
  • the methods of the invention are useful for removing the cations and ate-complex anions of metals, including but nto limited to cobalt, nickel, lead, cadmium, zinc, mercury, iron, chromium, silver, gold, cadmium, iron, palladium, platinum, gadolinium, uranium, and arsenic. Cations may be of any oxidation state commonly found in groundwater or industrial waste streams.
  • ate-complex anions refers to water-soluble complex anions, such as chloridate ions and oxyanions, of the formula MX n " " 1 , where each X is independently oxygen, nitrate, cyanide, carboxylate, or halogen, n is i -6, and the negative charge m ranges from 1 to 6. Examples include, but are not limited to, arsenate, uranyl, chlroroaurate, and chloroplatinate ions.
  • the key process referred to as "dendrimer-enhanced filtration” (DEF), uses dendritic macromolecules, or dendrimers, and a filtration step to produce a filtered fluid.
  • the DEF process as shown in Figure 1, is structured around three unit operations: a reaction unit, a filtration unit, and a dendrimer recovery unit.
  • the reaction unit (103) the contaminated water or other fluid (102) is mixed with a solution of functionalized dendritic polymers (101) to carry out any of a number of specific reactions of interest, including metal ion chelation, organic compound solubilization, contaminant oxidation-reduction, contaminant hydrolysis, binding of anions, and microbial/viral disinfection.
  • the resulting solution is passed through a filter in the filtration unit (105), producing a quantity of treated fluid (106).
  • a pump, (104) or a plurality of pumps (not shown), may be used at a number of different stages of the process to promote flow of the reaction components to various regions of the system.
  • the contaminant laden dendrimer solutions are subsequently sent to an optional dendrimer recovery unit (107), where the dendritic polymers, and if desired, the contaminants that were bound to the dendrimers (108), are recovered.
  • the recycled dendrimers may be recycled back into the reaction unit (109).
  • the recovered contaminants may be otherwise disposed of or utilized.
  • system (100) refers to the overall DEF process, which may have any number or combination of some or all of the components described above or hereafter.
  • Dendrimers are particularly useful molecules for this purpose. Unlike micellar surfactant solutions, aqueous solutions of dendritic polymers contain globular nanostructures that are held together by covalent bonds. Because of their monodispersity and stable globular shape over a broad range of solution pH and background electrolyte concentration, the leakage of dendritic polymers through filtration membranes with an appropriate molecular weight cut-off (MWCO) is highly improbable. Dendritic polymers also have much less tendency to pass through filtration membranes than linear polymers of similar molar mass because of their much lower polydispersity and persistent globular shape. In particular, unlike a linear polymer, a dendrimer molecule cannot adopt an extended conformation and snake through the pores of a membrane.
  • MWCO molecular weight cut-off
  • Dendritic polymers can be designed to incorporate a wide variety of different functional groups that facilitate binding and/or reaction with a wide range of different type of contaminants.
  • Table 1 shows some examples of different types of dendrimer reactive groups and their target contaminants; this list is by no means exhaustive.
  • dendrimer refers to 3-D globular macromolecules that may have three covalently bonded components: a core, interior branch cells and terminal branch cells.
  • dendrimers include hyperbranched polymers, dendrigraft polymers, tecto-dendrimers, core- shell(tecto)dendrimers, hybrid linear-dendritic copolymers, dendronized polymers, dendrimer-based supramolecular assemblies and dendrimer-functionalized solid particles.
  • Figure 2 shows some examples of different types of dendrimers. They may be functionalized with surface groups that make them soluble in appropriate media or facilitate their attachment to appropriate surfaces. They may be bioactive dendrimers, as later defined herein.
  • dendrimer agent refers to a chemical composition containing dendrimers.
  • the dendrimer agent may comprise a single dendrimer with a single functionality, a single dendrimer with multiple functionalities, a mixture of dendrimers, dendrimers that have been cross-linked to other dendrimers (tecto-dendrimers, or megamers), and dendrimers that have been covalently linked to linear polymers to produce linear-dendritic copolymers or dendronized linear polymers.
  • a dendrimer agent may also include buffers, salts, stabilizers or inert ingredients, and may be provided in a number of forms, including but not limited to solids, solutions, suspensions, gels, semi-liquids, and slurries. As will be recognized by one of skill in the art, there is a variety of different dendrimer agent compositions that would be suitable for the system and would therefore fall within the scope of the present invention.
  • PAMAM poly(amidoamine) dendrimer with an ethylene diamine (EDA) core.
  • EDA ethylene diamine
  • PAMAM dendrimers possess functional nitrogen and amide groups arranged in regular "branched upon branched" patterns which are displayed in geometrically progressive numbers as a function of generation level ( Figure 2).
  • the high density of nitrogen ligands enclosed within a nanoscale container makes PAMAM dendrimers particularly attractive as high capacity chelating agents for metal ions in aqueous solutions.
  • PAMAM dendrimers may be used to develop efficient, cost effective and environmentally-acceptable chelating agents for removing arsenic, cadmium, chromium, copper, lead, mercury and fluoride ion from contaminated water.
  • NH 2 -terminated G3, G4 and G5 PAMAM dendrimers with an ethylene diamine (EDA) core may be reacted with the appropriate reagents to build PAMAM dendrimers with various terminal groups that are optimizable and have binding specificities that target toxic metal ions and inorganic contaminants.
  • the dendrimer terminal groups may include hydroxide, acetamide, carboxylate, phosphonate, sulfonate and quaternary amine (methyl).
  • the chemical compositions of the surface modified dendrimers may be monitored by FTIR/ I3 C NMR spectroscopy and size exclusion chromatography.
  • the molar masses of the surface modified PAMAM dendrimers may be determined by matrix assisted laser desorption (MALD I)-time of flight (TOF) mass spectrometry (MS) and gel electrophoresis.
  • MALD I matrix assisted laser desorption
  • TOF time of flight
  • MS mass spectrometry
  • a system for carrying out the process of DEF may comprise a number of different components or units.
  • the term "reaction unit” refers to a component of a water filtration system where dendrimers and contaminated water are mixed.
  • the reaction unit may contain a single type of dendrimer, or a mixture of different types of dendrimers, as well as multifunctional dendrimers.
  • the dendrimers and the contaminated water undergo a reaction, such as binding or catalysis, and the reaction unit may be subjected to conditions that facilitate a such a reaction. Such conditions include but are not limited to elevated or reduced temperature and elevated or reduced pH.
  • contaminated water refers to water that contains at least one solute which the practitioner desires to separate from the water.
  • the value to the practitioner may lie in the purified water, in the separated solute, or both.
  • solutes may, for example, comprise a substance, the presence of which renders the water unfit for consumption, use in an industrial process, or disposal into a waterway.
  • solutes may also comprise a substance that is of commercial value when isolated from solution, such as a metal present in an industrial waste water stream or in a solution-mining leachate or lixiviant fluid.
  • Possible substances include but are by no means limited to metal ions, anions, organic compounds, bacteria, viruses, and biological compounds such as proteins, carbohydrates, and nucleic acids.
  • Contaminants are often toxic metals and chemicals found in the environment that need to be removed from water in order to make it potable.
  • Examples of toxic compounds that may be removed or treated by a DEF system include, without limitation, copper, perchloroethelene, perchlorate, arsenic (arsenite and arsenate), chromium (chromate), and lead.
  • the term "treated” or "filtered” water refers to water from which at least one contaminant has been removed or catalytically modified.
  • filtration unit refers to a component of a water filtration system wherein contaminated water that has been contacted with a dendrimer agent is filtered such that water and free solutes pass through a filter, but dendrimers and dendrimers with bound solutes are retained. It may also be referred to as a "clean water recovery unit”.
  • the filter in the filtration unit is referred to as the “filtration unit filter”.
  • the solution that passes through the membrane is referred to as the "filtrate”.
  • the goal of the filtration unit is to produce "clean" water; water from which a measurable, and preferably a substantial amount of at least one contaminant have been removed by the dendrimers. It is within the scope of the application to have the reaction unit integrated with the filtration unit.
  • integrated refers to multiple components that are mechanically interconnected such as in a single physical unit.
  • filter refers to an entity that is often a physical barrier, that retains some molecules or compounds while allowing others to pass through. In most cases, the selection of what passes through the filter is based on size; for example, a filter retains larger compounds and molecules while allowing smaller ones to pass through.
  • An example of a simple size-based filter is a porous membrane.
  • Membrane-based systems may be suitable for use in DEF, as a membrane may be used that has a smaller pore size than the dendrimers, so that dendrimers and any dendrimer-bound contaminants are retained by the membrane, while water from which the contaminants have been removed passes through as a filtrate.
  • An alternative type of filter is one in which the filtering entity is in contact with a solid support or matrix.
  • dendrimers may be attached to or deposited on a surface of a solid matrix.
  • the chemistry of the terminal groups may be used to either covalently or non-covalently attach the dendrimers to a solid support. Contaminated water is provided to the dendrimer/matrix assembly, and binding of the contaminants to the dendrimer occurs. Water from which at least a portion of the contaminants have been removed is produced.
  • Solid-supported filters may include a number of different dendrimers and dendrimer types, including but in no way limited to cation/anion selective ligands, redox active metal ions and clusters, catalytically active metal ions and clusters, hydrophobic cavities, and bioactive agents.
  • An example of a solid-supported filter is shown in Figure 3.
  • filter encompasses but is not limited to membranes and solid-support filters. It is also possible that a system has both a membrane filter and a solid supported filter in the same unit, or in separate units operated in parallel or in series.
  • the filtration process which separates the free dendrimers and contaminant-bound dendrimers from the filtered water, may be driven by pressure, vacuum, or gravity. If pressure is used, it may be applied to the side of the membrane containing the dendrimers to increase the flow of filtrate through the membrane. Pressure may be generated by the appplication of gas pressure, or may be mechanically applied, for example by pistons or by the action of a centrifuge. A vacuum may be applied to the side of the membrane opposite of the dendrimer-containing side, to increase the flow rate from the other side of the membrane. Filtration may also be driven by the hydrostatic pressure provided by gravity, and combinations of applied pressure, vacuum, and hydrostatic pressure may be used.
  • the pore size of the filter may vary, and will be appropriate to the size and type of the dendrimers used in the system.
  • suitable filters are nanofilters, used for nanofiltration (NF), ultrafilters, used for ultrafiltration (UF), and microfilters, used for microfiltration (MF).
  • Nanofilters may have a pore size that is less than about 2 nanometers (nm) in diameter.
  • Ultrafilters may have a pore size ranging from about 2 to 20 nm, which may be useful for non-cross-linked dendrimers.
  • Microfilters may have membranes with pores larger than 20 nm, which may be particularly useful for retaining cross-linked dendrimers (tecto-dendrimers) or megamers. In general, the larger pore size of MF membranes allow a faster flow rates than the UF and NF membranes.
  • the "dendrimer recovery unit” or “recycling unit” is a component of a water filtration system wherein at least a portion of the solutes that were bound to dendrimers earlier in the process are separated from the dendrimers, producing a quantity of unbound dendrimers and a quantity of solutes. Following removal of the solutes from the dendrimers, the dendrimers may be re-used in future rounds of water filtration. The removed solutes may be discarded in a waste stream, or isolated to the degree required for safe disposal or for use as a resource.
  • the term "recycling reaction” refers to any process by which contaminant-bound dendrimers are recycled, recovered, regenerated, or otherwise returned to a state that is useful for binding contaminants.
  • the un-bound dendrimers may be subjected to a recycling reaction along with the contaminant-bound dendrimers.
  • the type of recycling reaction used depends on the nature of the interaction between the contaminant and the dendrimer.
  • Recycling processes suitable for various dendrimer types are described below; although one of skill in the art will readily recognize a number of variations and additional processes that may be readily implemented, and are considered to be within the scope of the present invention.
  • the recycling reaction may take place in the dendrimer recovery unit, or in an integrated system, such as one where the filtration unit and the dendrimer recovery unit share the same membrane or filter.
  • the dendrimers may not be possible or desirable to recycle the dendrimers.
  • the compounds that are bound in the dendrimers in the reaction unit are radioactive, or pose some other sort of environmental hazard, it may be desirable for the contaminant-bound dendrimers to be used once and then processed as waste.
  • filtration unit and the dendrimer recovery unit are integrated, or are a single unit.
  • a single membrane may used in both processes.
  • the same unit may be subjected to different conditions to promote either retention or recovery of contaminants.
  • DEF processes and systems have the potential to be flexible, reconfigurable, and scalable.
  • the process is scalable; it is limited only by very few factors (e.g., by the size of or number of filters or membranes) as will be readily appreciated by those of skill in the art.
  • the flexibility of DEF is illustrated by its adaptability to a modular design approach.
  • DEF systems may be designed to be "hardware invariant" and thus reconfigurable in most cases by simply changing the dendrimer agent and dendrimer recovery system for the targeted contaminants.
  • DEF may be used in small mobile membrane-based water treatment systems as well as larger and fixed treatment systems and a host of other commercial, residential, and industrial applications.
  • Dendrimer-enhanced filtration is a useful tool for removing cations from aqueous solutions, particularly metal ions.
  • DEF has been shown to be more effective than polymer-supported ultrafiltration (PSUF) at recovering metal ions such as Cu(II) from contaminated water (Diallo, M. S. et al. (2005), Envir. ScL Technol, 39: 1366- 1377).
  • Metal ion complexation is an acid-base reaction that depends on several parameters including (i) metal ion size and acidity, (ii) ligand basicity and molecular architecture and (iii) solution physical-chemical conditions.
  • Three important aspects of coordination chemistry are the Hard and Soft Acids and Bases (HSAB) principle, the chelate effect and the macrocyclic effect (Martell and Hancock, (1996) Metal Complexes in Aqueous Solutions; Plenum Press: New York.).
  • the HSAB principle provides "rules of thumb” for selecting an effective ligand (i.e., Lewis base) for a given metal ion (i.e., Lewis acid).
  • Table 2 shows the binding constants of metal ions to selected unidendate ligands.
  • the OH " ligand is representative of ligands with negatively charged "hard” O donors such as carboxylate, phenolate, hydroxymate, etc.
  • NH 3 is representative of ligands with "hard” saturated N donors (e.g. aliphatic amines); whereas imidazole is representative of "border line” hard/soft ligands with unsaturated N donors.
  • the mercaptoethanol group (HOCH 2 CH 2 S " ), on the other hand, is representative of ligands with "soft” S donors such as thiols.
  • Table 2 shows that soft metal ions such Hg(II) and Au(I) tend to form more stable complexes with ligands containing S donors. Conversely, hard metal ions such Fe(III) tend to prefer hard ligands with O donors; whereas borderline hard/soft metal ions such as Cu(II) can bind with soft/hard ligands containing N, O and S donors depending on their specific affinity toward the ligands.
  • the chelate effect is predicated upon the fact that metal ions form thermodynamically more stable complexes with ligands containing many donor atoms than with unidentate ligands.
  • the macrocyclic effect highlights the fact that metal ions tend to form thermodynamically more stable complexes with ligands containing preorganized cavities lined with donors (i.e., Lewis bases) than with multidendate and unidentate ligands (Martell and Hancock, (1996) Metal Complexes in Aqueous Solutions; Plenum Press: New York.).
  • Dendritic macromolecules provide ligand architecture and coordination chemistry for metal chelation. Although macrocyles and their open chain analogues (unidentate and polydentate ligands) form stable complexes with a variety of metal ions, their limited binding capacity (1 :1 complexes in most cases) is a major impediment to their utilization as high capacity chelating agents for environmental separations such as water purification. Their relatively low molecular weights also preclude their effective recovery from wastewater by low cost membrane-based techniques (e.g., ultrafiltration and nanofiltration).
  • PAMAM poly(amidoamine) dendrimers from Dendritic Nanotechnologies (DNT) and Dendritech
  • ASTRAMOLTM poly(propyleneimine) imines (PPI) dendrimers from DSM as high capacity chelating agents, metal ion contrast agent carriers for magnetic resonance imaging, and templates for the synthesis of metal-bearing nanoparticles with electronic, optical and catalytic activity.
  • dendritic polymers that could be used as metal ion chelating agents include the water-soluble phosphorous dendrimers available from Dendrichem, and the HYBRANETM polyester amide hyperbranched polymers from DSM. Also applicable to the present invention is the recent development of a "click chemistry" route for the synthesis of low cost PriostarTM dendrimers by DNT. According to DNT, this will allow the introduction and control of six critical nanostructure design parameters that may be used to engineer over 50,000 different major variations of sizes, compositions, surface functionalities and interior nanocontainer spaces.
  • PriostarTM dendrimers may provide a broad range of low-cost and high capacity/selectivity recyclable dendritic chelating agents for water purification; they are suitable for use in connection with alternate embodiments of the present invention and are thus considered to be within the scope thereof.
  • Table 3 provides a list of some, but not all, commercially available dendritic polymers that may be used as high capacity and recyclable chelating agents for water purification by dendrimer-enhanced filtration in accordance with various embodiments of the present inventions. Table 3:
  • dendritic polymers that may be used as high capacity and recyclable chelating agents for water purification by dendrimer enhanced filtration
  • Dendritic macromolecules can serve as stable and covalently-bonded micelle mimics, having hydrophobic interiors that can encapsulate organic solutes in aqueous and nonaqueous solutions (Zeng F. and Zimmerman, S. (1997), Chem. Rev., 1681., Bosman, A. W., et al. (1999), Chem. Rev., 99:1665, Tomalia, D. A., et al. PNAS, 99:5081-5087).
  • Dendritic macromolecules such as PAMAM dendrimers can also solubilize organic compounds through specific interactions with their amino groups. KJeinman et al. (Kleinman, M. H., et al. (2000), J. Phys.
  • dendrimer agents may be suitable for use in a DEF system that is configured to remove organic solutes from aqueous solution.
  • Table 4 lists some manufacturers that produce dendrimers that may be used.
  • Dendrimers that are useful in this system may have a hydrophobic core, or hydrophobic exterior, as well as a hydrophilic core or a hydrophilic exterior.
  • the uptake of organic solutes by dendritic macromolecules in aqueous solutions may occur through several mechanisms including: 1. hydrophobic partitioning into the micellar core/shell, 2. hydrogen bonding to the macromolecule internal and terminal groups and 3. specific interactions with the macromolecule internal and terminal groups.
  • the recycling reaction for organic compound-binding may vary according to how the compounds are bound to the dendrimer.
  • Some possible recycling processes include but are not limited to 1) air stripping or vacuum extraction of the bound organic solutes, 2) pervaporation of the bound organic solutes, 3) release of the bound organic solutes by protonation or deprotonation of the dendritic micelle mimics followed by UF or NF and 4) extraction of the bound organic solutes using a solvent.
  • dendritic macromolecules that may be used as dendritic micelle mimics for water purification by dendrimer enhanced filtration (DEF).
  • the present invention provides an alternative to ion exchange resins for the treatment of ClO 4 " contaminated water.
  • the method of the invention combines functionalized ClO 4 - binding dendritic nanomaterials with membrane-based separation technologies such as ultrafiltration (UF).
  • UF ultrafiltration
  • the G5-NH 2 PPI dendrimer has a molar a molar mass of 7168 Da and a hydrodynamic radius (R h ) of 1.98 ran, and can be effectively separated from aqueous solutions by UF.
  • the maximum EOB of ClO 4 " to G5-NH 2 PPI dendrimer in aqueous solutions at pH 4.0 is -9.0; this corresponds to a binding capacity of 125 mg of ClO 4 " per g of dendrimer.
  • the invention also provides a method for removal of perchorate from water containing interfering ions such as sulfate, by contacting the water with a mixture of two or more dendrimers.
  • at least one dendrimer has an affinity for perchlorate, while each additional dendrimer has an affinity for at least one interfering ion.
  • This method may be used to effectively recover perchlorate from aqueous solutions containing high concentrations of interfering anions such as SO 4 2" .
  • the method of the invention is amenable to recycling and re-use, because at pH 9.0 to 11.0 there is rapid and nearly complete release of ClO 4 " from the the G5-NH 2 PPI dendrimer. This is a significant improvement over the use of C10 4 " -selective ion exchange resins, which are not readily regenerated.
  • Dendrimers in a dendrimer-enhanced filtration system may also be used to facilitate oxidations, reductions, or other chemical transformations of contaminants in water.
  • Pollutants in groundwater include chlorinated alkenes such as perchloroethylene (PCE), poly(nitroaromatics) such as trinitrotoluene (TNT), and redox active metals and anions such as Cr(VI) and NO 3 .
  • PCE perchloroethylene
  • TNT trinitrotoluene
  • redox active metals and anions such as Cr(VI) and NO 3 .
  • Most of these compounds may undergo catalytic reductive and oxidative transformations in aqueous solutions, which presents opportunities for remediation based on catalysis of such transformations.
  • Functionalized dendrimers that promote such transformations may be used as reactive media for remediation of groundwater and surface water contaminated by organic and inorganic solutes.
  • redox refers to chemical reactions that involve the loss or gain
  • a number of redox-active dendritic catalysts have been synthesized and characterized that would be useful in a DEF water filtration system. These include dendrimers with ferrocene terminal groups that can oxidize glucose or reduce nitrates, carbosilane dendrimers with diaminoarylnickel(II) terminal groups which can catalyze the Karsch addition of tetrachloromethane to methacrylate, and complexes of Cu(Il), Zn(II) and Co(III) with poly(propyleneimine) dendrimers that catalyze the hydrolysis of p-nitrophenyl diphenyl phosphate (a simulant for chemical warfare agents such as Sarin.)
  • a number of dendritic catalytic systems have also been successfully implemented in continuous membrane reactors (Astruc and Chardac, (2001) Chem. Rev. 101 :2991).
  • dendrimers as nanoscale metal ion containers to synthesize metal bearing nanoparticles with catalytic properties
  • These nanoparticles commonly referred to as dendrimer nanocomposites, can be efficiently prepared by reactive encapsulation, a process that involves the complexation of guest metal ions followed by their reduction and immobilization inside a dendritic host and/or at its surface.
  • the inventor has shown the use of the Fe(0)/Fe(II) and Fe(II)/Fe(III) redox systems to develop water soluble and solid-supported dendritic nanoparticles to demonstrate the potential usefulness of dendrimer nanocomposites and transition metal ion-dendrimer complexes in water purification.
  • the Fe(0)/Fe(II) and Fe(II)/Fe(III) redox couples can drive the oxidative and reductive transformations of a variety of organic and inorganic solutes.
  • Reactions of relevance to water purification of water include the reductive dehalogenation of chlorinated hydrocarbons such PCE, the reduction of Cr(VI) to Cr(III), and the oxidation of As(III) to As(V) in the presence of dissolved oxygen.
  • the initial focus was on the reductive dehalogenation of PCE by Fe(O) dendrimer nanocomposites in aqueous solutions (Example 4 includes data on the reduction of PCE by Fe(O) dendrimer nanocomposites).
  • the recycling reaction for redox active dendrimers may be accomplished by a number of means, including electrochemical regeneration.
  • the dendrimers may be placed in proximity to a an electrode, or redox couple that has a reduction potential that is favorable to oxidize or reduce the dendrimer catalyst to the state required for further rounds of catalysis. This may be accomplished in an electrochemical cell, where an electrical current is applied, or by reacting the dendrimers with another redox-active metal.
  • different types of recycling processes may desriable, as will be readily appreciated by those of skill in the art.
  • a number of different redox-active dendrimer agents would be suitable for use in water filtration systems. Table 4 lists some commercially available dendrimers that may be used in the system.
  • the dendrimer-enhanced filtration process may also be used to remove anions from water.
  • Anions have emerged as major water contaminants throughout the world because of their strong tendency to hydrate.
  • the discharge of anions such as perchlorate (ClO 4 " ), pertechnetate (TcO 4 " ), chromate (CrO 4 2” ), arsenate (AsO 4 3” ), phosphate (HPO 4 2” ) and nitrate (NO 3 " ) into publicly owned treatment works, surface water, groundwater and coastal water systems is having a major impact on water quality.
  • anions Unlike cations, anions have filled orbitals and thus do not readily bind to or coordinate with ligands. Anions do have a variety of geometries, however, and in many cases are sensitive to solution pH, so that shape-selective and pH-responsive receptors can be used to target anions. Because the charge-to-radius ratios of anions are also lower than those of cations, anion binding to ligands through electrostatic interactions tends to be weaker than cation binding. Anion binding and selectivity also depend on anion hydrophobicity and solvent polarity.
  • the present invention provides methods useful for removing anions from water.
  • Dendrimer-bound groups that promote anion binding include but are not limited to alkyl amines, trialkyl amines, amide NH groups, and pyrrole NH groups.
  • Examples of anions that may be removed by a DEF process using anion-binding dendrimers include but are not limited to ClO 4 " , TcO 4 " , CrO 4 2" , AsO 4 3 , HPO 4 2 , and NO 3 " .
  • An example of how perchlorate (ClO 4 " ) may be separated from water is shown in the Examples.
  • Reagent grade sodium perchlorate (NaClO 4 ), sodium chloride (NaCl), sodium nitrate (NaNO 3 ), sodium bicarbonate (NaHCO 3 ) and sodium sulfate (Na 2 SO 4 ) from Sigma-Aldrich were used, respectively, as sources of ClO 4 ' , Cl “ , NO 3 ' , HCO 3 " and SO 4 2" .
  • Reagent grade nitrates of Co(II), Ag(I), Fe(III), and Ni(II) were used as sources of the metal ions.
  • G5-NH 2 PPI and G4-NH 2 PAMAM dendrimers in methanol solutions were purchased from Sigma- Aldrich and used as received.
  • Dendrimer concentrations were measured using a Shimadzu Model 1601 UV- Visible spectrophotometer at wavelength of 201 nm. Anion concentrations were determined by ion chromatrography (Dionex DX- 120 ion chromatograph, IonPac AS 16 analytical column, IonPac AG 16 guard column). Metal ion concentrations were determined by routine atomic absorption spectrophotometry. Details are described in Diallo, M. S. et al., (2004) Langmuir, 20:2640-2651, which is incorporated herein by reference.
  • PAMAM dendrimers with ethylene diamine (EDA) core and terminal NH 2 groups are synthesized via a two-step iterative reaction sequence that produces concentric shells of ⁇ - alanine units (commonly referred to as generations) around the central EDA initiator core ( Figure 4). Selected physicochemical properties of these dendrimers are given in Table 5.
  • CNN H2 Number of primary amine groups.
  • dpK.N ⁇ pKa of dendrimer tertiary amine groups.
  • epK-NH2 pKa of dendrimer primary amine groups.
  • R G dendrimer radius of gyration.
  • 8R H dendrimer hydrodynamic radius.
  • the EOB of a metal ion in aqueous solutions of a dendrimer is readily measured by (i) mixing and equilibrating aqueous solutions of metal ion and dendrimer, (ii) separating the metal ion laden dendrimers from the aqueous solutions by ultrafiltration (UF) and (iii) and measuring the metal ion concentrations of the equilibrated solutions and filtrates by atomic absorption spectrophotometry.
  • Table 6 compares the EOB of Cu(II) in aqueous solutions of EDA core Gx-NH 2 PAMAM dendrimers to the Cu(II) binding capacity of selected linear polymers with amine groups. On a mass basis, the EOB of Cu(II) to the Gx- NH 2 PAMAM dendrimers are much larger and more sensitive to solution pH than those of linear polymers with amine groups that have been used in previous PEUF studies.
  • Figure 5 provides evidence of the role of tertiary amine groups in the uptake of Cu(II) by EDA core PAMAM dendrimers in aqueous solutions.
  • Both the G4-NH 2 and G4-Ac EDA core PAMAM dendrimers have 62 tertiary amine groups with pKa of 6.75-6.85.
  • the G4-NH 2 PAMAM dendrimer has 64 terminal groups with pKa of 10.20.
  • the G4-Ac PAMAM dendrimer has 64 non ionizable terminal acetamide (NHCOCH 3 ) groups.
  • Figure 5 shows that no binding of Cu(II) occurs to the G4-NH 2 and G4-Ac PAMAM dendrimers at pH 5, where all the primary and tertiary amine groups of the dendrimers are protonated. Conversely, significant binding of Cu(II) is observed at pH 7.0 and 9.0.
  • This model expresses the EOB of Cu(II) in aqueous solutions (at neutral pH) Of Gx-NH 2 PAMAM dendrimers as function of metal ion-dendrimer loading (N Cu0 /N d ), number of dendrimer tertiary amine group (NjJ 1 ), number of water molecules bound to the dendrimers (N J120 11 ), metal ion amine group/bound water coordination numbers ( CN£ u(II).N and CNc 1100-J120 ) a °d the intrinsic association constants of Cu(II) to the dendrimer tertiary amine groups and bound water molecules (k£ u(I1) _ N and kc U( io- H2 o)-
  • Figure 6 highlights the results of a preliminary evaluation of the model.
  • the model provides a good fit of the measured EOB of Cu(II) for the G4-NH 2 PAMAM dendrimer.
  • the model also reproduces the increase in the EOB observed at higher metal ion-dendrimer loadings following the first plateau. Note that the two-site
  • the ⁇ £ u(II) _ N values for the G4-NH 2 and G5-NH 2 EDA core PAMAM dendrimers are respectively equal to 3.15 and 3.78.
  • the binding constants of Cu(II) to the tertiary amine groups of the Gx-NH 2 PAMAM dendrimers are comparable in magnitude to the formation constants of Cu(II)-ammonia complexes.
  • Table 7 also suggests that the Gx-NH 2 PAMAM dendrimers will selectively bind Cu(II) over first-row transition metal ions such as Co(II) and Ni(II) and alkaline earth metal ions in wastewater such as Na(I), Ca(II) and Mg(II).
  • the dendrimer-enhanced filtration process (Figure 1) is structured around two unit operations: 1. a clean water recovery unit and 2. a dendrimer recovery unit.
  • contaminated water is mixed with a solution of functionalized dendritic polymers (e. g., dendrimers, dendrigfrat polymers, hyperbranched polymers, core-shell tecto(dendrimers), etc) to carry out the specific reactions of interest (metal ion chelation in this case).
  • functionalized dendritic polymers e. g., dendrimers, dendrigfrat polymers, hyperbranched polymers, core-shell tecto(dendrimers), etc
  • UF experiments were carried out to measure the retention of dendrimers and Cu(II)- dendrimer complexes by model UF membranes.
  • the experiments were performed in a 10- mL stirred cell (Amicon, Model 8010) at an applied pressure of 450 kPa (65 psi). For each run, the initial volume was 1 L.
  • the stirred cell was operated for 4.5 hours with permeate collected every 30 minutes and flux measurements taken every 10 minutes.
  • Regenerated cellulose (RC) and polyethersulfone (PES) membranes were evaluated.
  • the RC and PES membranes had a diameter of 25 mm with molecular weight cut-off (MWCO) of 5000 Dalton (5 kD) and 10000 Dalton (10 kD).
  • MWCO molecular weight cut-off
  • the concentrations of the G3 -NH 2 (2.42265 10 "5 mole/L), G4-NH 2 (8.49762 10 '6 mole/L) and G5-NH 2 (5.31808 10 "6 mole/L) PAMAM dendrimers were kept constant in all experiments.
  • a Cu(II) concentration of 10 mg/L was used in all experiments.
  • the molar ratio of Cu(II) to dendrimer NH 2 groups was also kept constant at 0.2 in all experiments.
  • the Cu(II)-dendrimer solutions were maintained under constant agitation for 1 hour in the dispensing pressure vessel following adjustment of their pH with concentrated HCl or NaOH.
  • the pH of aqueous solutions of PAMAM dendrimers and their complexes with Cu(II) can be controlled within 0.1-0.2 pH unit by addition of concentrated NaOH or HCl.
  • concentrations of metal ion in the feed and permeate were determined by atomic absorption spectrophotometry. Solute retention (R) was expressed as:
  • Figure 7 highlights the effects of dendrimer generation and membrane chemistry on the retention of EDA core Gx-NH 2 PAMAM dendrimers in aqueous solutions at pH 7.0 and room temperature.
  • the retentions of the G5-NH 2 PAMAM dendrimer by the 10 kD regenerated cellulose (RC) and polyethersulfone (PES) membrane are > 97% in all cases.
  • Such high retention values are expected for the G5-NH 2 EDA core PAMAM dendrimer, a globular macromolecule with a low polydispersity and a molar mass of 28826 Dalton (Table 5). Retentions greater than 90% were also observed for the G4-NH 2 PAMAM dendrimer ( Figure 7).
  • This dendrimer is also globular in shape and has very low polydispersity with a molar mass (14215 Dalton) greater than the MWCO of the 10 kD RC and PES membranes (Table 5). Possible explanations for the initial low retention ( «73%) of this dendrimer by the 10 kD PES membrane include measurement errors and/or the presence of impurities such as unreacted EDA and other lower molar mass reaction by-products in the G4-NH 2 PAMAM dendrimer sample.
  • Figure 7 also shows that the retentions of the G3-NH 2 EDA core PAMAM dendrimer are lower than those of the higher generation dendrimers.
  • This dendrimer has the lowest molar mass (Table 5).
  • Table 5 For both membranes, there is a significant retention of the G3-NH 2 dendrimer even though the MWCO of the dendrimers are 45% larger than the dendrimer molar mass (6906 Dalton).
  • the retention of the G3-NH 2 dendrimer by the 10 kD RC membrane ( Figure 7) is comparable to that of a linear polyethyleneimine (PEI) polymer with an average molar mass of 50 to 60 kD (4).
  • PEI linear polyethyleneimine
  • the MWCO is usually defined as the molar mass of a globular protein with 90% retention.
  • R H the slightly higher R H values could be attributed for the most part to dendrimer hydration. Because the differences in the retentions of the EDA core Gx-NH 2 PAMAM dendrimers are (for the most part) comparable to the differences between their radii of gyration and hydrodynamic diameter, R G /R H appears to be a better indicator of dendrimer retention by UF membranes in aqueous solutions.
  • Figure 8 highlights the effects of solution pH, membrane chemistry and MWCO on the retention of aqueous complexes of Cu(II) with a G4-NH 2 EDA core PAMAM dendrimer at room temperature.
  • a Cu(II) concentration of 10 mg/L (0.00016 mole/L) was used in all experiments.
  • the molar ratio of Cu(II) to dendrimer NH 2 groups was also kept constant at 0.2 to ensure that all the Cu(II) ions will be bound to the tertiary amine groups of the Gx-NH 2 PAMAM dendrimers at pH 7.0.
  • Figure 8 illustrates the effects of dendrimer generation on the retention of Cu(II)- dendrimer complexes by the 10 kD membranes at pH 7.0.
  • the observed retention values are consistent with the results of the dendrimer retention measurements ( Figure 7).
  • Higher retention values are observed for the complexes of Cu(II) with the G5-NH2 PAMAM dendrimer.
  • smaller retention values for the Cu(II)-dendrimer complexes are observed with the G3-NH2 PAMAM dendrimer ( Figure 8).
  • Figure 8 shows significant retentions of Cu(II) complexes with the G3-NH2 dendrimer (86-89 % for the 10 kD RC membrane and 80-97% for the 10 kD PES membrane) even though the MWCO of each membrane is 45% larger than the dendrimer molar mass.
  • Fouling is a major limiting factor to the use of membrane based processes in environmental and industrial separations.
  • a characteristic signature of membrane fouling is a reduction in permeate flux through a membrane during filtration.
  • the permeate fluxes of aqueous solutions of Cu(II) complexes with Gx-NH 2 PAMAM dendrimers through RC and PES membranes at pH 7.0 and 4.0 were measured.
  • the Cu(II) concentration (10 mg/L) and molar ratio of Cu(II) to dendrimer NH 2 groups (0.2) were also kept constant.
  • Figure 9 shows the permeate fluxes through the RC and PES membranes.
  • the permeate flux shows little change over the course of the filtration varying from 124.0 to 116.0 L m "2 h "1 .
  • a similar behavior is also observed at pH 4.0.
  • the permeate fluxes are approximately 16% higher.
  • the permeate fluxes through the 5 kD RC membranes also exhibit little variation (49.0-43.0 L m "2 h '1 ) during the course of the filtration at pH 7.0 and 4.0.
  • Figure 9 also shows that dendrimer generation does not significantly affect the permeate flux through the 10 kD RC membrane.
  • Figure 10 shows a decline in the normalized permeate fluxes for both the RC and PES membranes during the filtration of aqueous solutions of Cu(II) complexes with Gx-NH 2 PAMAM dendrimer at pH 7.0.
  • a small decline in the relative permeate flux (7 to 18%) is observed.
  • the decrease in relative permeate flux (46 to 81%) is much larger for the PES membranes.
  • pH 4.0 a significant decrease in permeate flux (13 to 68%) is observed for the PES membranes.
  • membrane fouling may be caused by (i) concentration polarization resulting from solute accumulation near a membrane surface, (ii) pore blockage by solute sorption onto the surface of a membrane or within its pores and (iii) the formation of a cake layer by sorption/deposition of solutes on a membrane surface.
  • concentration polarization resulting from solute accumulation near a membrane surface
  • pore blockage by solute sorption onto the surface of a membrane or within its pores
  • solutes on a membrane surface a cake layer by sorption/deposition of solutes on a membrane surface.
  • the first model is a pore blockage model that expresses the decline in the normalized permeate flux as an exponential decay function. This model did not provide a good fit of the data (results not shown).
  • the second model expresses the decline in the normalized permeate flux as a power-law function (Zeman, L. J. et al., (1996) Microfiltration and Ultrafiltration. Principles and Applications; Marcel Dekker: New York, and Kilduff, J. E. et al., (2002) Env. Eng. ScL 19:477-495.):
  • n values for the G3-NH 2 and G5-NH 2 PAMAM dendrimers membranes are, respectively, equal to 0.45 ⁇ 0.05 and 0.30 ⁇ 0.02 for thelO kD PES membranes at pH 7.0.
  • Zeeman and Zydney Zeman, L. J. et al., (1996) Microfiltration and Ultrafiltration, Principles and Applications; Marcel Dekker: New York.
  • Kilduff et al. Karlduff, J. E. et al., (2002) Env. Eng. Sci. 19:477-495.
  • G3-NH 2 1O kD 7.0 2.74+0.75 0.4510.05 0.037 a k and n are determined by fitting the measured relative permeate fluxes to Equation 4. Goodness of fit parameter.
  • the goodness of fit parameter is defined as where y is the fitted value, y, is the measured value and ⁇ , is the estimated standard deviation for y,.
  • PEUF Polymer enhanced ultrafiltration
  • the metal ion binding capacity of an ideal polymer for PEUF should also exhibit sensitivity to stimuli such as solution pH over a range broad enough to allow efficient recovery of the metal and recycling of the polymer.
  • An ideal polymer for PEUF should also be non-toxic and stable with a long life cycle to minimize polymer consumption.
  • the Cu(II) binding capacities of the Gx-NH 2 PAMAM dendrimers are much larger and more sensitive to solution pH (Table 6) than those of linear polymers with amine groups.
  • Table 7 shows that Na(I), Ca(II) and Mg(II) have very low binding affinity toward ligands with N donors such as NH 3 .
  • the high concentrations of Na(I), Ca(II) and Mg(II) found in most industrial wastewater streams are not expected to have a significant effect on the Cu(II) binding capacity and selectivity of NH 2 PAMAM dendrimers.
  • Example 3 Use of dendrimer enhanced filtration (DEF) to remove anions
  • the dendrimers used were fifth generation (G5-NH 2 ) poly(propylene) (PPI) dendrimer with a diaminobutane (DAB) core and terminal NH 2 groups.
  • PPI poly(propylene)
  • DAB diaminobutane
  • the binding assay procedure consisted of (i) mixing and equilibrating aqueous solutions of perchlorate and dendrimer at room temperature, (ii) separating the perchlorate- dendrimer complexes from the aqueous solutions by ultrafiltration and (iii) measuring the concentration of perchlorate in the equilibrated solutions and filtrates.
  • Figure 15 shows the EOB of perchlorate in aqueous solutions of the G5-NH 2 PPI dendrimer as a function of anion-dendrimer loading and solution pH. In these experiments, the molar ratio of anion- dendrimer NH 2 group was varied to prepare solutions with a given perchlorate dendrimer loading.
  • the EOB of perchlorate to the G5-NH 2 PPI dendrimer was measured after an equilibration time of 30 minutes, compared to 24 hours for the ion exchange resin.
  • the fast binding kinetics of dendrimers are an expected advantage of homogenous liquid phase processes such as DEF.
  • the concentrations of perchlorate in the solutions [ClO 4 l and filtrates [ClO 4 I were measured using a Dionex DXl 20 ion chromatograph with conductivity suppression and detection.
  • the ClO 4 " detection limit was ⁇ 4 ppb.
  • the concentration of bound perchlorate [ClO 4 I (mole/L) was expressed as:
  • the EOB (moles of bound perchlorate per mole of dendrimer), the concentration of dendrimer [ C d ] (mole/L) in solution and the fractional binding [FB] (%) were expressed as: m.
  • m d (g) is the mass of dendrimer in solution
  • V s (L) is the solution volume
  • M wd (g/mole) is the dendrimer molar mass (Table 9).
  • Figures 16 and 17 show the effects of anion- dendrimer loading and solution pH on the EOB and FB of CKV to a G5-NH 2 PPI dendrimer in deonized water at room temperature and reaction time of 1 hour.
  • the molar ratio of perchlorate to dendrimer was varied to prepare solutions with a given anion- dendrimer loading.
  • Three replicate measurements were carried out in each set of experiments; to preserve the clarity of the figures, only duplicate measurements are plotted.
  • Figure 16 shows that the EOB of perchlorate goes through a series of distinct binding steps at pH 4.0 as anion-dendrimer loading increases.
  • Each successive perchlorate binding step involves an initial increase of solute binding followed by a second increase, this behavior is attributed to the presence of dendrimer sites with different binding capacity and affinity for ClO 4 " .
  • ClO 4 " guest ions diffuse into the interior of the dendrimer host to occupy its internal and confined cavities. This nonspecific mode of guest uptake by a macromolecular host is referred to as "topological trapping" in the supramolecular chemistry literature.
  • the maximum EOB of ClO 4 " decreases by a factor of 4 at pH 7.0 compared to that at pH 4.0.
  • the maximum EOB Of ClO 4 " is also smaller at pH 9.0 even though -81% of the dendrimer NH 2 groups remain protonated.
  • Figure 16 also shows some binding OfClO 4 " at pH 11.0 [with a maximum EOB ⁇ 1.29 at anion-dendrimer loading of 32.0], where virtually all amines of the G5-NH 2 PPI dendrimer are unprotonated.
  • This "residual" binding may be attributed to topological trapping Of ClO 4 " anions in the hydrophobic interior of the PPI dendrimer.
  • Perchlorate has a larger ionic radius and hydration free energy than most anions present in groundwater and surface water.
  • dendrimers with hydrophobic cavities and positively charged internal groups might selectively bind ClO 4 " over more hydrophilic anions such as Cl “ , NO 3 " , SO 4 2” and HCO 3 " .
  • This dendrimer has the same number of tertiary amine and primary groups than the G5-NH 2 PPI dendrimer.
  • the extents of protonation of the tertiary and primary amine groups of the PPI and PAMAM dendrimers are comparable (Table 9).
  • the G4-NH 2 PAMAM dendrimer is more hydrophilic, having 64 additional internal amide groups that can interact with water through hydrogen bonding.
  • Molecular dynamics simulations of Gx-NH 2 PAMAM dendrimers with explicit water molecules carried out by Goddard and co-workers (30) showed extensive water penetration in the interior of a G4-NH 2 PAMAM dendrimer. Niu et al.
  • Example 4 Use of DEF to remove target anions in the presence of interfering anions To assess the effects of competing anions on perchlorate uptake by the G5- NH2 PPI dendrimer, the uptake of perchlorate by a G5-NH 2 PPI dendrimer was studied in model electrolyte solutions containing the potentially interfering ions Cl “ , NO 3 " , HCO 3 " and SO 4 2" .
  • the low background electrolyte (Electrolyte 1) consisted of a solution of 0.1 mM NaCl, 0.3 mM NaHCO 3 , 0.1 mM NaNO 3 and 0.1 mM Na 2 SO 4 with an initial molar ratio of SO 4 2" to ClO 4 " equal to 10.0.
  • the high background electrolyte (Electrolyte 2) consisted of a solution of 1.0 mM NaCl, 3.0 mM NaHCO 3 , 1.0 mM NaNO 3 and 1.0 mM Na 2 SO 4 with an initial molar ratio of SO 4 2" to ClO 4 " equal to 100.0.
  • Figure 19 compares the uptake of perchlorate by the G5-NH 2 PPI dendrimer in deonized water and electrolytes.
  • the maximum EOB (-6.0) decreases by a factor of 1.5 compared to that observed in deonized water (-9.0) at pH 4.0.
  • Figure 19 shows a large decrease of the maximum EOB of perchlorate (-2.0) in the high background electrolyte solution compared to that observed in deionized water (-9.0) at anion-dendrimer loading of -32.0.
  • the maximum EOB of perchlorate in deionized water (-2.20) is comparable to that in the low background electrolyte solution (-1.95).
  • Figure 22 shows the extent of binding and fractional binding of Fe(III) in aqueous solutions of G4-NH 2 EDA core PAMAM dendrimer at pH 7.0. Data were obtained using procedures shown by Diallo et al. (2004) Langmuir. 20:2640. These data indicate that most or all of the Fe is bound to the dendrimers.
  • Fe(O) (zero valent iron) nanocomposites were prepared by reduction of aqueous complexes of Fe(III) with a generation 4 (G4-NH 2 ) polyamido(amine) (PAMAM) dendrimer with ethylene diamine (EDA) core and terminal NH 2 groups at pH 7.0.
  • the overall process involves adding Fe(III) to the interior of dendrimers and reducing the Fe(III) to Fe(O) with a reductant such as sodium borohydride, producing dendrimers having Fe(O) deposited inside.
  • the process leaves the surface groups of the dendrimers unmodified so that they can be used for other reactions, such as attachment to a solid surface.
  • the resulting Fe(O) nanocomposite comprises Fe(O) nanoparticles dispersed within the dendrimer.
  • the utility of the nanocomposite was demonstrated by using the Fe(O) nanocomposite to reductively dehalogenate perchloroethylene (PCE).
  • Fe(O) PAMAM dendrimer nanocomposites The synthesis of Fe(O) PAMAM dendrimer nanocomposites was carried in 8 mL borosilicate glass vials at pH 7.0 by reacting 4 mL of aqueous solutions Fe(III)-dendrimer complexes with excess sodium borohydride (2000 ppm).
  • GC gas chromatography
  • ECD electron capture detector
  • FID flame ionization detector
  • the Fe(0)-containing nanocomposites are used to convert PCE to trichloroethylene (TCE) ( Figure 23A).
  • the control reaction ( Figure 23B) contains Fe(O) but no dendrimers.
  • Preliminary investigations showed significant reduction of PCE (40-60% after 3 hours) by the Fe(O)-PAMAM dendrimer nanocomposites.
  • only 20% of the 10 ppm of PCE was reduced in aqueous solutions in the control Fe(O) particles synthesized by reduction of 94 ppm Fe(III) with 2000 ppm of sodium borohydride.

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Abstract

L'invention concerne des compositions et des procédés utiles pour la purification de fluides aqueux en utilisant des macromolécules dendritiques. Le procédé comprend l'utilisation de macromolécules dendritiques (dendrimères) pour se lier à des solutés ou pour transformer chimiquement des solutés, ainsi qu'une étape de filtration destinée à obtenir le fluide duquel les solutés ont été éliminés ou transformés chimiquement. Comme exemples de dendrimères qui peuvent être utilisés dans le procédé, on peut citer les dendrimères qui se lient aux cations, les dendrimères qui se lient aux anions, les dendrimères qui se lient aux composés organiques, les dendrimères à action rédox, les dendrimères qui se lient aux composés biologiques, les dendrimères catalytiques, les dendrimères biocides, les dendrimères qui se lient à des virus, les dendrimères multifonctionnels et leurs mélanges. Le procédé est facilement évolutif et offre de nombreuses options de personnalisation.
PCT/US2007/024656 2006-10-23 2007-11-29 Traitement de l'eau par filtration améliorée par des dendrimères Ceased WO2008136814A2 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10329179B2 (en) 2009-09-18 2019-06-25 The Texas A&M University System Zero valent iron systems and methods for treatment of contaminated wastewater
US10377648B2 (en) 2009-09-18 2019-08-13 The Texas A&M University System Selenium removal using aluminum salt at conditioning and reaction stages to activate zero-valent iron (ZVI) in pironox process
US11084742B2 (en) 2014-12-19 2021-08-10 The Texas A&M University System Activated hybrid zero-valent iron treatment system and methods for generation and use thereof

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US20040072937A1 (en) * 2001-02-10 2004-04-15 Tomalia Donald A. Nanocomposites of dendritic polymers
EA200700335A1 (ru) * 2004-07-16 2007-12-28 Калифорния Инститьют Оф Текнолоджи Обработка воды с использованием фильтрации, улучшенной дендримерами

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10329179B2 (en) 2009-09-18 2019-06-25 The Texas A&M University System Zero valent iron systems and methods for treatment of contaminated wastewater
US10377648B2 (en) 2009-09-18 2019-08-13 The Texas A&M University System Selenium removal using aluminum salt at conditioning and reaction stages to activate zero-valent iron (ZVI) in pironox process
US11208338B2 (en) 2009-09-18 2021-12-28 Evoqua Water Technologies Llc Selenium removal using aluminum salt at conditioning and reaction stages to activate zero-valent iron (ZVI) in pironox process
US11084742B2 (en) 2014-12-19 2021-08-10 The Texas A&M University System Activated hybrid zero-valent iron treatment system and methods for generation and use thereof

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